1. Field of the Invention
The present invention relates generally to a method and apparatus for eliminating multi-user interference in a multi-antenna system, and more particularly, to a method and apparatus for eliminating multi-user interference in a multi-user multi-antenna system, which maintain strength against quantization noise and fast fading environments.
2. Description of the Related Art
Due to the rapid growth of the mobile communication market, a variety of wireless multimedia services are required. Research is being conducted to provide high-capacity and high-rate data transmission, and a multi-antenna system (e.g., a Multiple Input Multiple Output (MIMO) system) that can efficiently use limited frequency resources.
In comparison with a single-antenna system, the multi-antenna system can achieve high transmission reliability and a high data rate without the allocation of additional frequency and transmission (TX) power. This is due to the fact that it transmits data by using an independent channel for each antenna. Specifically, the multi-antenna system can improve system performance through a diversity gain and can improve the data rate through a multiplexing gain. The multi-antenna system can also expand to a multi-user multi-antenna system that supports multi-user environments.
The multi-user multi-antenna system can further increase the frequency efficiency because multiple user terminals share spatial resources secured through multiple antennas.
In order to prevent interference between user terminals, a Base Station (BS) of the multi-user multi-antenna system precodes downlink signals prior to transmission to the user terminals. The user terminals acquire their respective information from signals received through their respective channels. For example, the BS may use a Zero Forcing (ZF)-based or Minimum Mean Square Error (MMSE)-based precoding scheme to reduce multi-user interference. The BS may also use a Dirty Paper Coding (DPC)-based or Block Diagonalization (BD)-based precoding scheme to reduce multi-user interference while satisfying system channel capacity. As described above, the BS precodes TX signals to eliminate interference between user terminals that use the same subchannel.
A scheme that prevents performance degradation caused by a quantization error in the precoding operation is under active discussion. Accordingly, conventional precoding schemes are designed to consider a quantization error in a multi-user multi-antenna system. However, because most of the conventional quantization precoding schemes presuppos slow fading or flat fading, if they are used in fast fading environments caused by mobile stations, performance degradation may occur due to a quantization error caused by the mismatching between a quantization codebook and a channel.